CN100340540C - Method for preparing aromatic diamine derivatives - Google Patents

Abstract

The present invention discloses a method for efficiently preparing an aromatic diamine derivative represented by the following formula (3) with high yield, which includes reacting an aromatic amide represented by the following formula (1) with an aromatic halide represented by the following formula (2) . (Wherein Ar, Ar ¹ and Ar ² represent a substituted or unsubstituted aryl group or heteroaryl group; Ar ³ represents a substituted or unsubstituted arylene group or heteroarylene group; X represents a halogen atom).

Description

Method for preparing aromatic diamine derivatives

technical field

The present invention relates to a novel method for preparing aromatic diamine derivatives; more particularly, to a method for aromatic diamine derivatives useful as charge transport materials for electrophotographic photoconductors or materials for organic electroluminescent devices.

Background technique

Aromatic diamine compounds have been used as charge transport materials for electrophotographic photoconductors or materials for organic electroluminescence (EL) devices. Especially in the case where an aromatic diamine compound is used as an organic EL device material, when the device material does not have a high glass transition temperature, the resulting organic EL device cannot exhibit heat resistance. Therefore, many attempts have been made to develop aromatic diamine derivatives containing a large number of aromatic rings (such as benzene rings or heterocyclic rings) in the molecule.

However, aromatic diamine derivatives generally containing a large number of aromatic rings in the molecule show very poor solubility in solvents, and this low solubility causes problems, including precipitation of diamine molecules in the solvent during the reaction and limited reaction yield. For example the following response:

It is difficult to proceed due to the low solubility of the starting materials and reaction intermediates due to the presence of a large number of intramolecular aromatic rings.

Aromatic diamine derivatives are known to be prepared by reaction routes using starting materials such as α-naphthylamine, β-naphthylamine, 4-aminobiphenyl or p-diaminobiphenyl which are compounds known to exhibit mutagenicity. The production of these compounds called "Special Chemical Substances" is prohibited in Japan, and therefore, there is a need to provide a production method that does not use the compounds as raw materials or intermediates.

For example, as an example of the production method, International Application PCT/JP02/02132 describes a method for producing an aromatic amine by reacting an aromatic amine having an aralkyl group (such as a benzyl group) with an aromatic halide without using Starting materials or intermediates showing mutagenicity as described above.

However, difficulties were encountered in determining the conditions for the above reaction because the reaction required a reduction reaction (eg, hydrogenation) upon removal of the aralkyl group, which often resulted in reduction of the aromatic ring (ie, a side reaction).

invention disclosure

In order to solve the above-mentioned problems, an object of the present invention is to provide methods for producing aromatic diamine derivatives useful as charge transport materials for electrophotographic photoconductors or materials for organic EL devices, which can be produced in high yields in an efficient manner.

In order to achieve the above object, the present inventors have carried out extensive research and found that when an aromatic amine with a specific structure reacts with an aromatic halide with a specific structure, the aromatic diamine derivative can be produced in an effective manner with high yield preparation. Based on this finding, the present invention has been accomplished.

Therefore, the present invention provides a method for preparing an aromatic diamine derivative represented by the following formula (3), the method comprising reacting an aromatic amide represented by the following formula (1) with an aromatic halide represented by the following formula (2):

(wherein Ar represents a substituted or unsubstituted aryl group with 6-30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group with 5-30 ring carbon atoms; each Ar ¹ and Ar ² represent a group with 6 - a substituted or unsubstituted aryl group with 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group with 5-30 ring carbon atoms; Ar ³ represents a substituted or unsubstituted group with 6-30 ring carbon atoms Arylene, or a substituted or unsubstituted heteroarylene having 5-30 ring carbon atoms; X represents a halogen atom).

The best way to invent

The present invention will be described in detail below.

In the present invention, Ar represents a substituted or unsubstituted aryl group having 6-30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having 5-30 ring carbon atoms. Examples of aryl groups include phenyl, biphenyl, terphenyl, naphthyl, anthracenyl, phenanthrenyl, pyrenyl, chrysyl and fluoranthenyl. Examples of heteroaryl groups include pyrrolyl, furyl, thienyl, triazolyl, oxadiazolyl, pyridyl and pyrimidinyl. Among them, phenyl, biphenyl and naphthyl are particularly preferable.

In the present invention, each of Ar ¹ and Ar ² represents a substituted or unsubstituted aryl group having 6-30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having 5-30 ring carbon atoms. Examples of aryl groups include phenyl, biphenyl, terphenyl, naphthyl, anthracenyl, phenanthrenyl, pyrenyl, chrysyl and fluoranthenyl. Examples of heteroaryl groups include pyrrolyl, furyl, thienyl, triazolyl, oxadiazolyl, pyridyl and pyrimidinyl. Among them, phenyl, biphenyl and naphthyl are particularly preferable.

In the present invention, Ar ³ represents a substituted or unsubstituted arylene group having 6-30 ring carbon atoms, or a substituted or unsubstituted heteroarylene group having 5-30 ring carbon atoms. Examples of the arylene group include phenylene, biphenylene, terphenylene, naphthylene, anthracenylene, phenanthrene, pyrenylene, chrylenylene, and fluoranthenylene. Examples of the heteroarylene group include pyrrolylene, furylylene, thienylene, triazolylene, oxadiazolylidene, pyridinylene and pyrimidinylene. Among them, phenylene, biphenylene and naphthylene are particularly preferable.

Examples of substituents present in Ar and Ar ¹ -Ar ³ include aryl groups having 5-30 ring carbon atoms, C1-C12 alkyl or alkoxy groups and aryl groups having 5-30 ring carbon atoms Substituted amino groups.

Examples of C1-C12 alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, cyclopentyl, n-hexyl, cyclohexyl and adamantane base.

Examples of C1-C12 alkoxy include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentyloxy, cyclopentyloxy group, n-hexyloxy, cyclohexyloxy and adamantyloxy.

The number of substituents present in Ar ¹ -Ar ³ is preferably 0-4.

In the present invention, X represents a halogen atom, and examples of the halogen atom include iodine, bromine, chlorine and fluorine, particularly preferably iodine and bromine.

The production method of the present invention is used in the case where the total number of benzene rings and/or heterocycles contained in the aromatic diamine derivative represented by formula (3) is 8 or less, especially in the case where the total number is 10 or more.

In the production method of the present invention, it is preferable to react the aromatic amide represented by the formula (1) with the aromatic halide represented by the formula (2) in the presence of a transition metal compound-forming catalyst.

Examples of transition metals include Mn, Fe, Co, Ni, Cu, Pd, Mo, Rh, Ru, V, Cr, Pt, Ir and Zn, among which Ni, Pd, Pt, Zn and Cu are preferred, and Cu is more preferred.

Examples of the transition metal compound form include transition metal fine powder, transition metal halide, transition metal oxide and transition metal chalcogenide, preferably transition metal halide. Examples of halides include fluoride, chloride, bromide and iodide, with bromide and iodide being particularly preferred. Preference is given to using zero-valent or monovalent transition metal compounds.

The amount of the catalyst to be added is usually 0.01 to 1 equivalent, preferably 0.1 to 0.5 equivalent, relative to the above-mentioned aromatic halide.

Preferably, the aromatic amide represented by formula (1) and the aromatic halide represented by formula (2) are carried out in the presence of a base. The base employed is preferably a hydroxide or an alkali metal or alkaline earth metal salt, among hydroxides and salts, hydroxides, carbonates, bicarbonates and acetates are preferred, more preferably hydroxides of strong bases .

The amount of the base to be added is usually 2 to 5 equivalents, preferably 2 to 3 equivalents, relative to the above-mentioned aromatic halide.

The reaction solvent used during the reaction between the aromatic amide represented by formula (1) and the aromatic halide represented by formula (2) is preferably a hydrocarbon compound because the reaction requires high-temperature heating in the presence of a strong base. In particular, it is preferable to use a solvent having a high boiling point, and examples of usable solvents include xylene, decahydronaphthalene, dioxane, dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), preferably xylene and decalin.

Before use, the solvent is preferably subjected to dehydration or inert gas replacement, and dehydration or inert gas replacement of the solvent can be performed by techniques generally used for organic solvents. For example, a desiccant such as calcium chloride may be added to the solvent, or the solvent may be distilled in the presence of calcium hydride or sodium metal under a flow of eg nitrogen or argon.

In the present invention, the above-mentioned reaction temperature is usually room temperature - 150°C, preferably 100-150°C. The reaction time is 1-48 hours, preferably 6-18 hours. The reaction process (including catalyst preparation) is preferably carried out under an inert gas atmosphere.

Examples of aromatic amides represented by formula (1) used in the preparation method of the present invention include N, N-bis-(4-biphenyl)benzamide, N-(1-naphthyl)-N-phenylbenzamide amides, N-(2-naphthyl)-N-phenylbenzamide and N-(1-naphthyl)-N-(4-biphenyl)benzamide.

Examples of the aromatic halide represented by the formula (2) used in the production method of the present invention include 4,4'-diiodobiphenyl, 1,4-diiodobenzene, 4,4"-diiodo-p-terphenyl, 4 , 4'-dibromobiphenyl, 1,4-dibromobenzene, 4,4"-dibromo-p-terphenyl.

Examples of the aromatic diamine represented by the formula (3) prepared by the preparation method of the present invention include N, N, N', N'-tetrakis(4-biphenyl)-p-diaminobiphenyl and N,N'-bis( 1-phenyl)-N,N'-diphenyl-4,4'-p-diaminobiphenyl.

The aromatic diamine derivative produced by the production method of the present invention is useful as a charge transport material of an electrophotographic photoconductor or a material of an organic EL device.

The present invention will be described in more detail later by examples, which should not be construed as limiting the present invention.

Embodiment 1 (N, N, N', the preparation of N'-four (4-biphenyl) p-diaminobiphenyl)

(1) N, the synthesis of N-bis (4-biphenyl) benzamide

4-Bromobiphenyl (product of Tokyo Kasei Kogyo Co., Ltd.) (10.0 g), benzamide (product of Tokyo Kasei Kogyo Co., Ltd.) (2.31 g), cuprous iodide (Kanto Kagaku product) (0.36 g) and anhydrous potassium carbonate (Kanto Kagaku product) (5.8 g) were charged in a 100 mL three-necked flask. The flask was then fitted with a stirrer, rubber caps (septa) on each side neck of the flask and a screw reflux condenser on the central neck. Install a three-way stop valve and a balloon containing argon on the reflux condenser. The atmosphere of the reaction system was replaced with argon in a balloon by using a vacuum pump (this process was performed three times).

Subsequently, diethylbenzene (50 mL) was added through a rubber septum by using a syringe, the flask was placed in an oil bath, and the resulting mixture was gradually heated to 200°C with stirring. After 6 hours, the flask was removed from the oil bath to complete the reaction. The flask was then placed under an argon atmosphere for 12 hours.

The resulting reaction mixture was transferred to a separatory funnel, and dichloromethane (100 mL) was added to the mixture, thereby dissolving a precipitate in the mixture. After the mixture was washed with saturated brine (60 mL), the obtained organic layer was dried over anhydrous potassium carbonate. Potassium carbonate was separated by filtration, and the solvent of the obtained organic layer was removed by evaporation. Toluene (200 mL) and ethanol (40 mL) were added to the obtained residue, and the obtained mixture was heated to 80° C. while using a drying tube, thereby completely dissolving the residue in the mixture. The mixture was then allowed to stand for 12 hours and gradually cooled to room temperature for recrystallization.

The formed crystals were separated by filtration and dried in vacuo at 60° C. to obtain 7.22 g of N,N-bis(4-biphenylyl)benzamide.

(2) N, N, N', the synthesis of N'-tetrakis (4-biphenyl) p-diaminobiphenyl

N,N-bis(4-biphenyl)benzamide (1.00 g), 4,4'-diiodobiphenyl (product of Wako Pure Chemical Industries, Ltd.) (0.45 g), cuprous iodide (0.021 g) and potassium hydroxide (0.51 g) were added to a 50 mL two-necked flask. Rubber caps (septa) were then installed on each side neck of the flask and a screw reflux condenser on the central neck. Install a three-way stop valve and a balloon containing argon on the reflux condenser. The atmosphere of the reaction system was replaced by argon contained in a balloon using a vacuum pump (this process was performed three times).

Subsequently, toluene (20 mL) was added through a rubber septum by using a syringe, the flask was placed in an oil bath, and the resulting mixture was gradually heated to 140°C with stirring. After the mixture was stirred at 140°C for 6 hours, the flask was removed from the oil bath and allowed to stand at room temperature for 12 hours.

The precipitated product was completely dissolved in dichloromethane (50 mL), and the resulting solution was transferred to a separatory funnel. After the solution was washed with saturated brine (50 mL), the separated organic layer was dried over anhydrous potassium carbonate. After filtering the organic layer, the solvent was removed by evaporation, and to the obtained residue were added toluene (150 mL) and ethanol (50 mL). The resulting mixture was heated to 80°C while using a drying tube to dissolve the residue in the mixture, and then gradually cooled to room temperature. The resulting precipitate was then isolated by filtration, washed with a little toluene and ethanol. Subsequently, the solution precipitate was dried with a vacuum dryer at 60°C for 3 hours to obtain 0.72 g of N,N,N',N'-tetrakis(4-biphenylyl)-p-diaminobiphenyl.

NMR (nuclear magnetic resonance spectrum), FD-MS (field desorption mass spectrometry) and HPLC (high performance liquid chromatography) were carried out to the obtained N, N, N', N'-tetrakis (4-biphenyl) p-diaminobiphenyl Measurement, the measurement results are as follows.

NMR: δ90MHz 7.1-7.8 (44H, m)

FD-MS: 792, 396

HPLC: chemical purity 99.6% or above

The total reaction yield was 73%.

Comparative example 1 (N, N, N ', the preparation of N'-tetrakis (4-biphenyl) p-diaminobiphenyl: by the route of different embodiment 1)

(1) N, the synthesis of N-bis (4-biphenyl) benzylamine

4-Bromobiphenyl (product of Tokyo Kasei Kogyo Co., Ltd.) (10.0 g), sodium tert-butoxide (product of Wako Pure Chemical Industries, Ltd.) (4.32 g) and palladium acetate (product of Wako Pure Chemical Industries , Ltd.) (42mg) into a 100mL three-necked flask. The flask was then fitted with a stirrer, rubber caps (septa) on each side neck of the flask and a screw reflux condenser on the central neck. Install a three-way stop valve and a balloon containing argon on the reflux condenser. The atmosphere of the reaction system was replaced with argon in a balloon by using a vacuum pump (this process was performed three times).

Subsequently, dehydrated toluene (product of Wako Pure Chemical Industries, Ltd.) (60 mL), benzylamine (product of Tokyo KaseiKogyo Co., Ltd.) (2.04 mL) and tri-tert-butylphosphine (product of Aldrich product, 2.22 mol/L toluene solution) (169 μL), and the resulting mixture was stirred at room temperature for 5 minutes.

The flask was then placed in an oil bath, and the resulting mixture was gradually heated to 120°C with stirring. After 7 hours, the flask was removed from the oil bath to complete the reaction. The flask was then placed under an argon atmosphere for 12 hours.

The resulting reaction mixture was transferred to a separatory funnel, and dichloromethane (300 mL) was added to the mixture, thereby dissolving a precipitate in the mixture. After the mixture was washed with saturated brine (60 mL), the obtained organic layer was dried over anhydrous potassium carbonate. Potassium carbonate was separated by filtration, and the solvent of the obtained organic layer was removed by evaporation. Toluene (200 mL) and ethanol (40 mL) were added to the obtained residue, and the obtained mixture was heated to 80° C. while using a drying tube, thereby completely dissolving the residue in the mixture. The mixture was then allowed to stand for 12 hours and gradually cooled to room temperature for recrystallization.

The formed crystals were separated by filtration and dried in vacuo at 60° C. to obtain 6.73 g of N,N-bis(4-biphenylyl)benzylamine.

(2) Synthesis of two-(4-biphenyl)amine

N,N-bis(4-biphenyl)benzylamine (1.35 g) obtained in (1) above was mixed with palladium/activated carbon (product of Wako Pure Chemical Industries, Ltd., palladium content: 10%wt%) (135 mg) was put into a 300 mL single-necked flask, chloroform (100 mL) and ethanol (20 mL) were added to the flask, and these substances were dissolved in the solvent.

The flask was then fitted with a stirrer and a three-way stop valve with a balloon filled with hydrogen (2 L) was fitted. The atmosphere in the flask was replaced with hydrogen by using a vacuum pump (this process was performed 10 times). The balloon is filled with fresh hydrogen to supplement the hydrogen consumed above. After the hydrogen volume was restored to 2 L, the solution in the flask was vigorously stirred at room temperature for 30 minutes. Subsequently, dichloromethane (100 mL) was added to the solution, and the catalyst was removed by filtration.

The resulting solution was then transferred to a separatory funnel, and the solution was washed with saturated aqueous sodium bicarbonate (50 mL). Then, the obtained organic layer was separated, dried with anhydrous potassium carbonate, and after filtering the organic layer, the solvent was evaporated, and methanol (50 mL) was added to the obtained residue to conduct recrystallization. The formed crystals were separated by filtration and dried under vacuum at 50°C to obtain 0.99 g of bis(4-biphenylyl)amine.

(3) N, N, N', the synthesis of N'4-tetrakis (4-biphenyl) p-diaminobiphenyl

Bis(4-biphenyl)amine (0.500 g), 4,4'-dibromobiphenyl (product of Tokyo Kasei Kogyo Co., Ltd.) (0.231 g) obtained in (2) above, palladium acetate (0.0034g) and potassium tert-butoxide (0.157g) into a 50mL two-necked flask. Rubber caps (septa) were then installed on each side neck of the flask and a screw reflux condenser on the central neck. Install a three-way stop valve and a balloon containing argon on the reflux condenser. The atmosphere of the reaction system was replaced by argon contained in a balloon using a vacuum pump (this process was performed three times).

Subsequently, dehydrated toluene (10 mL) and tri-tert-butylphosphine (Aldrich product, 2.22 mol/L toluene solution) (13.4 μL) were added through a rubber septum by using a syringe, the flask was placed in an oil bath, and the resulting mixture was gradually stirred under stirring. Heat to 115°C. After the mixture was stirred at 115°C for 6 hours, the flask was removed from the oil bath and allowed to stand at room temperature for 12 hours.

The precipitated product was completely dissolved in dichloromethane (500 mL), and the resulting solution was transferred to a separatory funnel. After the solution was washed with saturated brine (100 mL), the separated organic layer was dried over anhydrous potassium carbonate. After filtering the organic layer, the solvent was removed by evaporation, and to the obtained residue were added toluene (150 mL) and ethanol (50 mL). The resulting mixture was heated to 80°C while using a drying tube to dissolve the residue in the mixture, and then gradually cooled to room temperature. The resulting precipitate was then isolated by filtration, washed with a little toluene and ethanol. Subsequently, the solution precipitate was dried with a vacuum dryer at 60°C for 3 hours to obtain 0.453 g of N,N,N',N'-tetrakis(4-biphenylyl)-p-diaminobiphenyl.

The obtained N, N, N', N'-tetrakis(4-biphenyl)-p-diaminobiphenyl was measured by NMR, FD-MS and HPLC, and the measurement results were as follows.

NMR: δ90MHz 7.1-7.8 (44H, m)

FD-MS: 792, 396

HPLC: chemical purity 99.5% or above

The total reaction yield is 63%.

Comparative Example 2 (N, N, N', the preparation of N'-tetra(4-biphenyl)-diaminobiphenyl: the Ar in which formula (1) is the situation of methyl)

(1) N, the synthesis of N-bis (4-biphenyl) acetamide

4-Bromobiphenyl (product of Tokyo Kasei Kogyo Co., Ltd.) (10.0 g), sodium tert-butoxide (product of Wako Pure Chemical Industries, Ltd.) (4.32 g) and palladium acetate (product of Wako Pure Chemical Industries , Ltd.) (42mg) into a 100mL three-necked flask. The flask was then fitted with a stirrer, rubber caps (septa) on each side neck of the flask and a screw reflux condenser on the central neck. Install a three-way stop valve and a balloon containing argon on the reflux condenser. The atmosphere of the reaction system was replaced with argon in a balloon by using a vacuum pump (this process was performed three times).

Subsequently, dehydrated toluene (product of Wako Pure Chemical Industries, Ltd.) (60 mL), acetamide (product of Tokyo KaseiKogyo Co., Ltd.) (1.24 g) and tri-tert-butylphosphine (product of Aldrich product, 2.22 mol/L toluene solution) (169 μL), and the resulting mixture was stirred at room temperature for 5 minutes.

The flask was then placed in an oil bath, and the resulting mixture was gradually heated to 120°C with stirring. After 7 hours, the flask was removed from the oil bath to complete the reaction. The flask was then placed under an argon atmosphere for 12 hours.

The resulting reaction mixture was transferred to a separatory funnel, and dichloromethane (300 mL) was added to the mixture, thereby dissolving a precipitate in the mixture. After the mixture was washed with saturated brine (60 mL), the obtained organic layer was dried over anhydrous potassium carbonate. Potassium carbonate was separated by filtration, and the solvent of the obtained organic layer was removed by evaporation. Toluene (200 mL) and ethanol (40 mL) were added to the obtained residue, and the obtained mixture was heated to 80° C. while using a drying tube, thereby completely dissolving the residue in the mixture. The mixture was then allowed to stand for 12 hours and gradually cooled to room temperature for recrystallization.

The formed crystals were separated by filtration and dried in vacuo at 60°C to obtain 0.91 g of N,N-bis(4-biphenylyl)acetamide.

(2) N, N, N', the synthesis of N'-tetrakis (4-biphenyl) p-diaminobiphenyl

Repeat the method of embodiment 1 (2), just with the N that above-mentioned (1) obtains, N-bis (4-biphenyl) acetamide (0.85g) replaces N, N-bis (4-biphenyl) benzene Formamide (1.00 g) to give 0.38 g of N,N,N',N'-tetrakis(4-biphenylyl)-p-diaminobiphenyl.

The obtained N, N, N', N'-tetrakis(4-biphenyl)-p-diaminobiphenyl was measured by NMR, FD-MS and HPLC, and the measurement results were as follows.

NMR: δ90MHz 7.1-7.8 (44H, m)

FD-MS: 792, 396

HPLC: chemical purity 99.3% or above

The overall reaction yield was 5%.

Industrial Applicability

As described above in detail, the method of the present invention enables the production of aromatic diamine derivatives useful as charge transport materials for electrophotographic photoconductors or materials for organic electroluminescent devices in an efficient manner with high yield.

Claims (7)

1. A method for preparing an aromatic diamine derivative represented by formula (3), the method comprising reacting an aromatic amide represented by formula (1) with an aromatic halide represented by formula (2):

wherein Ar represents a substituted or unsubstituted aryl group with 6-30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group with 5-30 ring carbon atoms; each Ar ¹ and Ar ² represent a group with 6- A substituted or unsubstituted aryl group with 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group with 5-30 ring carbon atoms; Ar ³ represents a substituted or unsubstituted group with 6-30 ring carbon atoms an arylene group, or a substituted or unsubstituted heteroarylene group having 5-30 ring carbon atoms; X represents a halogen atom. 2. The method for producing an aromatic diamine derivative as claimed in claim 1, wherein the aromatic diamine derivative represented by formula (3) contains 8 or more benzene rings and/or heterocycles in total. 3. The method for producing an aromatic diamine derivative as claimed in claim 1, wherein the aromatic amide represented by the formula (1) reacts with the aromatic halide represented by the formula (2) in the presence of a catalyst formed of a transition metal compound. 4. The process for producing aromatic diamine derivatives as claimed in claim 3, wherein the transition metal compound is a copper compound. 5. The method for producing aromatic diamine derivatives according to claim 1, wherein the aromatic amide represented by the formula (1) is reacted with the aromatic halide represented by the formula (2) in the presence of a base consisting of hydroxide. 6. The method for producing aromatic diamine derivatives as claimed in claim 5, wherein the hydroxide is an alkali metal hydroxide and/or an alkaline earth metal hydroxide. 7. The method for producing an aromatic diamine derivative as claimed in claim 1, wherein the reaction is carried out in a hydrocarbon compound used as a reaction solvent.